1. Field of the Invention
The present invention relates to an oxygen absorption resin composition that has excellent oxygen absorbency and does not emit unpleasant odor as a result of oxygen absorption.
2. Description of the Related Art
Gas barrier resins such as ethylene-vinyl alcohol copolymer (hereinafter also abbreviated as EVOH) are materials having excellent oxygen gas barrier properties and carbon dioxide gas barrier properties. Such a resin can be melt-molded and therefore is used preferably for a multilayered plastic packaging material comprising a layer of the resin laminated with a layer made of a thermoplastic resin (e.g., polyolefin, polyester, etc.) having excellent moisture-resistance, mechanical properties, and the like. However, the gas transmission of these gas barrier resins is not completely zero, and they transmit an amount of gas that cannot be ignored. It is known to use an oxygen absorbent in order to reduce transmission of such a gas, in particular, oxygen, which affects the quality of the content significantly, or in order to remove oxygen that already is present inside a packaging member at the time of packaging its content.
For example, as an improved oxygen absorbent, a composition comprising a transition metal catalyst and an ethylenically unsaturated compound (see Japanese Laid-Open Patent Publication No. 5-115776) and an oxygen scavenger that is a cross-linked polymer (see Japanese Laid-Open Patent Publication No. 11-70331) have been proposed. Furthermore, a resin composition containing EVOH as described above and an oxygen absorbent has been proposed (Japanese Laid-Open Patent Publication Nos. 2001-106866, 2001-106920 and 2002-146217). In particular, similarly to EVOH, the resin composition containing EVOH can be melt-molded and therefore can be used preferably for various packaging materials.
However, when the oxygen absorbent or the oxygen absorption resin composition as described above is used as a packaging material, the oxygen absorbent is decomposed as the oxygen absorption proceeds, and a unpleasant odor may be emitted. Furthermore, the mold-processability of the cross-linked polymers is poor, and therefore, when the polymers are kneaded with a thermoplastic resin, gels are produced, resulting in poor molding, and thus they cannot be put to practical use. In this way, there has been a demand for further improvement in applications in which fragrance is important.